Take away the stylistic excesses and the flamboyant imagery from se7en, Fight Club, and The Game and all that remains is someone obsessed with solving a puzzle. That’s what David Fincher has done in his latest, Zodiac: he’s cut out the flash and reduced the movie to the basics of a grimy character surrounded by piles of clues scratching his head.

The word “reduced” is misleading. This adaptation of Robert Graysmith’s account of the serial killer who stalked the San Francisco area in the ’60s and ’70s, taunting the police with coded notes and amassing a body count ranging from 5 to 37, clocks in at two and three-quarter hours. The slow passing of time — has Fincher been watching the films of Béla Tarr? — is broken by perfunctory outbursts of violence. It doesn’t so much bore as it frustrates. What exactly is going on? The story circles various possibilities: the bewilderment of the authorities, the terror of the populace, the bungling of bureaucracy. Not until well into its second hour does it settle on a theme: the need to know the truth, and the dismal toll of that futile obsession.

The object of the pursuit, Zodiac, won’t impress those jaded by the serial killers who have succeeded him in fact and fiction. Expect none of the baroque extravagances of Saw or Hostel; for Zodiac a simple bullet to the head or knife in the back will do. Brutal though they were, the killings themselves probably didn’t beguile Graysmith (Jake Gyllenhaal, shrunken into a sheepish nerd) into spending three decades trying to identify the culprit. It’s more likely that the crude cryptograms sent to the San Francisco Chronicle, where he was a cartoonist, first piqued his interest. Whatever the reason, he ends up alone among stacks of clutter in a room not unlike that of one of the prime suspects.

The official investigators fare little better. Chronicle crime reporter Paul Avery (Robert Downey Jr. in a showy performance), who’s flaky to begin with, ends up an alcoholic basket case living on a houseboat. San Francisco police inspector David Toschi (Mark Ruffalo as a duller Columbo) tries to pull the plug on his involvement before it’s too late. Each, like the movie itself, circles around possible solutions to the mystery, returning to the same promising, elusive leads, the same dead ends, pondered and discussed in ugly offices or fly-blown diners and bars.

Graysmith and Toschi finally meet at a screening of Dirty Harry, in which Eastwood’s iconic lawman pursues a Zodiac-like maniac and starts to take on some of the qualities of the killer himself. So too do the pursuers in Zodiac — not the homicidal sadism, but the repetition compulsiveness. So the film isn’t so much about killing as it is about time. Fincher indicates its passage with titles like “six hours later” or “four years later,” and they appear with such frequency and randomness that they grow as absurd as the nonsensical titles in Dalí & Buñuel’s L âge d’or. He marks one transition with a time-lapse view of the construction of the Transamerica Tower. The pieces all fit together; no such luck for the Zodiac investigators. Zodiac touches on a mystery less dramatic than the average serial-killer movie but more disturbing — how time passes while we try to make sense of past time.

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Dead flowers James Ellroy talks the way he writes, the way his doomed characters tell the stories of their lives: monotoned, terse, poetic, brutal. Peter Keough interviews James Ellroy (mp3)